Compressors, fans, turbines and like machinery employ rotors to which a plurality of blades are affixed. Such blades are arranged into one or more rows spaced axially along the rotor, the blades in each row being circumferentially arrayed around the periphery of the rotor.
As a result of the high steady and vibratory forces imposed on the blades during operation, the method of attaching the blades to the rotor requires careful design. One method of attachment employs generally axially extending grooves formed in the rotor periphery. The shape of the grooves may be that of a fir-tree, serrated, semi-circle, inverted T, or some variation thereof. Each blade has a corresponding root portion at its base which is closely profiled to match the shape of the rotor grooves. Each blade is retained in the rotor by sliding the root of the blade axially into a rotor groove. Blades affixed to the rotor in this manner are referred to as side entry blades. As a result of the close match in the size and shape of the blade root and the rotor groove, motion of the blade in the circumferential and radial directions is closely restrained. However, restraint of the blade in the axial direction, referred to as locking, requires a separate device. In the past, a variety of locking devices have been devised.
One such locking device comprises a locking device which is engaged in a circumferential slot between adjacent blades supported in axial grooves of a rotor. In an embodiment of the locking device, the locking device is formed with a key for engaging a slot in one of the blades and has a length shorter than the distance between the adjacent blades. A lug is formed on a side of the locking device opposite from the key, and a spacer is located in the circumferential slot and includes a lug adjacent to the lug on the locking device. The lugs on the locking device and the spacer are bent to engage each other and bias the locking device and spacer toward respective blades. Removal of the blades requires bending the lugs to a disengaged position, typically requiring that the locking device and spacer be scrapped and replaced by new components during blade replacement. Such a device is disclosed in U.S. Pat. No. 4,915,587, the entire disclosure of which is incorporated herein.